linux-kernel - Re: [PATCH v2] drm/simpledrm: Add support for multiple "power-domains"

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Date:   Tue, 19 Sep 2023 15:34:56 +0200
From:   "Sven Peter" <sven@...npeter.dev>
To:     "Thomas Zimmermann" <tzimmermann@...e.de>,
        "Janne Grunau" <j@...nau.net>,
        "Javier Martinez Canillas" <javierm@...hat.com>,
        "David Airlie" <airlied@...il.com>,
        "Daniel Vetter" <daniel@...ll.ch>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        asahi@...ts.linux.dev
Subject: Re: [PATCH v2] drm/simpledrm: Add support for multiple "power-domains"

Hi,


On Mon, Sep 18, 2023, at 09:11, Thomas Zimmermann wrote:
> Hi
>
> Am 12.09.23 um 22:22 schrieb Janne Grunau via B4 Relay:
>> From: Janne Grunau <j@...nau.net>
>> 
>> Multiple power domains need to be handled explicitly in each driver. The
>> driver core can not handle it automatically since it is not aware of
>> power sequencing requirements the hardware might have. This is not a
>> problem for simpledrm since everything is expected to be powered on by
>> the bootloader. simpledrm has just ensure it remains powered on during
>> its lifetime.
>> This is required on Apple silicon M2 and M2 Pro/Max/Ultra desktop
>> systems. The HDMI output initialized by the bootloader requires keeping
>> the display controller and a DP phy power domain on.
>> 
>> Signed-off-by: Janne Grunau <j@...nau.net>
>
> As a simpledrm patch:
>
> Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>
>
> Do you want to wait for another review from  someone with 
> power-management expertise?

I can't claim to have a lot of genpd experience but we use very similar
code in a few other M1/M2 drivers that also require multiple power domains
to be up without any sequencing constraints. So for whatever it's worth:

Reviewed-by: Sven Peter <sven@...npeter.dev>


Best,


Sven